Solvability in two dimensions, and subsequent passage from two dimensions to all dimensions, has been quite typical for progress in this subject.
One example, from the two-dimensional work of [1]} to the higher dimensional generalizations [2]} was mentioned earlier. In another example, the passage to higher dimensions
required the development
of major new ideas: the solvabilty
of the Dirichlet and Regularity problems in [3]} and [4]} came fifteen years after the two-dimensional results of [5]}, and used
the toolbox developed in connection with the solution to Kato's conjecture. The innovation in two dimensions that is applicable to the problem we solve
in this paper is a change of variable
observed by Feneuil in [6]} in another context, and is described in Section 4.
In Section 5, we present the new idea that leads to solvability of the Regularity problem in all dimensions \(n \ge 2\) .
